Help, Rough Running 98 Ls!

[Autofanatic]

ok, here goes.

for a while now, i have noticed my 98 ls400 running rough, particularly on cold mornings. it felt like the car was running on 7 cylinders. it used to always go away once the car warmed up, but now sometimes it doesnt. i was told to start with a tuneup and here is what i did.

changed air filter, spark plugs, fuel filter, pcv

i also cleaned the throttle body.

now, not only has my problem NOT been solved..but i am idling all over the place... started cold, the engine may idle at 1300 rpm!!!!

any suggestions for both problems???

[Darrell J]

Here are a few questions....

1. What kind of gasoline do you use.. Not all gas is the same... Cheap gas is cheap for a reason.. I know we all get cheap gas sometimes.. But its called cheap because it is a lower quality... And lexus is a higher quality car..

Also what octane level do you use...

2. What kind of spark plugs did you use? Brand.,,.

3. What kind of oil do you use

4. ARe you o-rings in good shape..

5 How about your cylinders.. are they clean looking and slightly greased on the wall

[RCRFAN3]

RCRFAN3 Dec 16 2006, 09:56 AM Post #1

Club Member

Group: Regular Member

Posts: 77

Joined: 8-April 03

From: Crystal lake IL

Member No.: 866

Car Model:1998 LS 400

Location:Crystal lake IL

I have a 98 LS400 with 130,000 miles on it. I started my car when it was 17 degrees(F) out and the car idled at 1500 RPM and continued to idle at this speed after car got to operating temp. I drove the car for 60 miles and the same thing occurred. I pulled my car into a heated garage and turned it off, and let it cool. I then restarted the car and since then the car has been operating normally, idling at 750 RPM. On a cold start, outdoor and motor temp, it idles at 1500 and has a very slight vibration to it. It feels like an oscillation of a motor or a possible flooder in the fuel system. It goes away after the engine warms up. I have been told that it is possibly the throttle control motor with magnetic clutch, or the same part called an IAC, idle air control valve. These are commonly replaced on American made cars, but I have found no such history for Lexus. Fuel mileage has not changed since I have experienced this. If you have had this problem or have any info for me, please respond.

[Autofanatic]

Ok, so after taking the car to two mechanics that told me they couldn't figure it out, I took the car to the dealer (blah). They called me today and said I have a broken motor mount and suggested i change the other motor mount and tranny mount at the same time. Cost = $850. At least it's not an engine problem...

[nc211]

Ok, so after taking the car to two mechanics that told me they couldn't figure it out, I took the car to the dealer (blah). They called me today and said I have a broken motor mount and suggested i change the other motor mount and tranny mount at the same time. Cost = $850. At least it's not an engine problem...

$850!! Ouch!! You take it to Johnson of Raleigh or the new one in Durham? If you were at the one in Raleigh last night, we probably passed eachother, as mine went in for an alighment/balance/rotation and a "once over" to make sure nothing is wrong. I've hit a few Jacuzzi sized potholes recently on my way to work.

[Autofanatic]

Took it to the new one in Durham. I am wondering now if I was raped by that price...

[nc211]

www.lexuspartsonline.com

mechanical / engine / mounts:

Front mounts "need two of them, one on left side, one on right side": $90 each

Rear mounts "aka..tranny mount" only need one: $32

Total in parts: $210. The tranny mount is easy as pie to do, the passenger side front motor mount is decent to do, the driver's side engine mount however is a pain in the AS$. That's were they probably had to spend the most time. Did you over pay? Yep, probably by $300-$400 in all. But, don't sweat it man, you've now learned the valuable lesson of the dealership... reserve it for truely complicated stuff, and in my opinion, balancing and alignments. They seem to nail the balancing and alignments everytime. Costs about an extra $50 buck, as I just had my tires rotated/balanced/aligned at the Raleigh location for $159 bucks. Plus, my mechanic guy who has helped me out several times, gives it a once-over review just to make sure. There isn't a sole who hasn't been hit by the dealerships prices at least once or twice on here, just part of the growing pains I guess. At least your repair is one that will last another 100k miles, which makes the price seem more justifyable. "God I can't spell this week"

If you're looking for a cheaper alternative, check out Phil's Toyshop in Cary. They specialize in only older Lexus and Toyota's, nothing else.